A ballast bed, which generally consists of weather-resistant hard rock (for example basalt) in various particle sizes depending on the track loading, is first formed for this track structure. The standard depth of ballast to the bottom edge of the sleeper is 30 cm. Rails or rail sections connected to concrete or wooden sleepers are placed on this ballast bed. Track-tamping machines are used to push ballast under the sleepers. These machines are equipped with hydraulically controlled picks which press the ballast under the sleepers. In order to allow rainwater to flow off and to prevent the rails lying under water, the ballast bed has to be regularly cleared of foreign matter. For this purpose, the ballast has to be lifted up, screened and then placed back on the track bed. It then has to be tamped again. Laying the rails and maintaining the track bed are therefore time-consuming and cost-intensive operations.